Recent successful investigations into CNS degeneration caused by prions demand that some important observations be exploited. To take advantage of these discoveries, we propose to develop several new and innovative approaches to transmissible neurodegenerative diseases utilizing some striking advances in molecular and biological techniques. Molecular genetic studies in mice and humans have shown that susceptibility to prion diseases - experimental scrapie in mice and Gerstmann-Straussler syndrome (GSS) in humans - is genetically linked to polymorphisms in the open reading frame (ORF) of the prion protein (PrP) gene. These polymorphisms results in non-conservative amino acid substitutions. Linkage of a PrP missense variant to the development of GSS established that GSS is a genetic disease which is also infectious and raises the possibility that the leucine variant at PrP codon 102 causes GSS. The need to learn more about human PrP gene polymorphisms in GSS and familial Creutzfeldt-Jakob disease (FCJD) is a utmost importance. Sequencing the ORF's of PrP genes from patients with GSS and FCJD is proposed. Sequencing of entire PrP genes from normal humans, patients with GSS, inbred mice with long and short incubation times sheep breeds with different susceptibilities to scrapie and several species of hamsters with distinct incubation times is planned. A search for prion diseases involving proteins other than PrP is proposed. The first candidate disease to be examined will be grey tremor (gt) of mice since gt appears to be both genetic and infectious like GSS. Studies are planned to create physical maps for mice and humans extending about 5 Mb on each side of the PrP gene. YAC clones will be recovered from libraries constructed with genomic DNA from mice and humans and used to create contig maps. Probes derived from these YAC clones will be employed to identify a linked scrapie incubation time gene (Prn-i_ in mice and the GSS gene in humans if these genes prove to be separable from the PrP gene. We plan to identify PrP related genes in mammals and in lower organisms using PCR amplication with primers constructed from highly conserved regions. Identification of authentic PrP-related genes in Drosophilia or C. elegans may greatly accelerate our studies since these organisms are readily amenable to genetic manipulation. The unprecedented discoveries in studies on prion diseases signal new directions in CNS degenerative disease research. The implications of discovering how prions cause neuronal dysfunction may be profound with respect to understanding Alzheimer's disease and some other neurodegenerative disorders of older people.